Boxing, otherwise known as wrapping, is the process of placing a primitive type within an object so that the primitive can be used as a reference object.

Autoboxing is the term for getting a reference type out of a value type just through type conversion (either implicit or explicit). The compiler automatically supplies the extra source code that creates the object.

For example, without autoboxing, the following code would not compile:

Without autoboxing, the Compiler would not accept the last line. Short are reference objects. To convert from a primitive integer value to a Short, you should "manually" instantiate the Short object. With autoboding, instead, the Compiler accepts the last line, and automatically transforms it so that a Short object is created to store the value 5.

Unboxing refers to getting the value that is associated to a given object, just through type conversion (either implicit or explicit). The Compiler automatically supplies the extra source code that retrieves the value out of that object, either by invoking some method on that object, or by other means.

For example, without unboxing, the following would not compile:

Without unboxing, the Compiler would not accept a comparison between a Short object and a primitive integer number. With unboxing, instead, the Compiler accepts the comparison and automatically transforms it so that a numeric value is extracted from the Short object.